util: fix compiler warning

conversion to 'wl_fixed_t {aka int}' from 'int64_t {aka long int}'
may alter its value [-Werror=conversion]
2 jobs for master in 2 minutes and 30 seconds (queued for 11 seconds)
Status Job ID Name Coverage
  Build
passed #1804371
build-native-autotools

00:02:30

passed #1804372
build-native-meson

00:00:49